1. Field of the Invention
This invention relates to a fungus preparation for control of weed trees.
More specifically the invention relates to a preparation of the fungus Chondrostereum purpureum, a method of producing such a preparation and to a method of treating weed trees with the preparation for the biological control of such trees.
2. Discussion of the Prior Art
Some trees in certain areas are considered to be unwanted or weed trees. It is frequently necessary to control the growth of selected tree species or selected trees in industrial right-of-ways and in reforestation areas without using toxic chemical herbicides. The control of red alder (Alnus rubra, Bong.) in reforestation areas is expensive in terms of weeding costs and lost growth potential. Other so-called weed trees include aspens (Populus tremuloides Michx.), beech (Fagus grandifolia Ehrh.), birches (Betula alleghaniensis Britt., papyrifera Marsh), maples (Acer macrophyllum Pursh., rubrum L), pin cherry (Prunus pensylvanica L.f.) and poplars (Populus balsamifera L.).
The common tree pathogen and wood rot fungus Chondrostereum purpureum (sometimes referred to hereinafter as C. purpureum) has been proposed as an effective biological control for the above-listed trees (see Wall, R. E., "The Fungus Chondrostereum purpureum as a Silvicide to Control Stump Sprouting in Hardwoods", Northern Journal of Applied Forestry 7:17-19). The fungus can kill meristematic tissues and prevent recovery through wood healing or stump sprouting. Because the fungus can be applied selectively, its use for control of the target trees or species of trees does not threaten the use of the same species for commercial or other purposes. However, the commercial production and application of C. purpureum as a biological control has been hindered by the lack of durable and easily produced reproductive structures (spores) and the fragile nature of the fungus mycelium. Actively growing mycelium of C. purpureum is a good source of inoculum for treating stumps and tree wounds for biological control However, maceration of the mycelium to facilitate application as a spray drastically reduces its viability. The fungus does not withstand drying, fragmentation and pelletization treatments which have been developed for other microbial products. The fungus has no dormant stage. There is a need for a formulation consisting of the fungus and non-toxic, biodegradable adjuvants. Cultures grown on whole or milled cereal grains are easily contaminated and overgrown by airborne molds. Chondrostereum purpureum is easily cultivated and stored on nutrient enriched soil substitutes such as vermiculite, but many such materials are too coarse to be applied as sprays or pastes. Coarse carriers are easily dislodged. Moreover, the unprotected mycelium applied to stumps and wounds is subject to desiccation and damage from ultraviolet radiation during the establishment period.